The purpose of this investigation is to evaluate the application of a direct current to stimulate bone ingrowth into porous aluminum oxide. Porous cylindrical samples will be implanted into the superior aspect of canine femora, and will reside in cancellous and cortical bone. Constant current power packs will also be implanted, active on one side and inactive on the opposite side as a control, and will maintain the implant site at a relative negative potential with respect to the surrounding soft tissue. The magnitude of the applied current will be monitored using a telemetry system. Tissue ingrowth will be evaluated using a mechanical push-out test, microradiography and histological thin sectioning. A protocol has been established whereby each method of evaluation can be performed on each implant. The interfacial shear strength and tissue microstructure will be studied as a function of implant residence site and implant residence time.